1. Field of the Invention
The present invention broadly relates to assessment of the optical quality of transparencies, such as helmet visors, and, more particularly, is concerned with a method of measuring spherical optical power and/or prismatic deviation of the transparency.
2. Description of the Prior Art
The Air Force provides protection of its pilots from secondary bird strike injuries by the use of a visor attached to the pilot's helmet. While there are military specifications for this visor, heretofore there has been no easily available, industry usable corresponding measurement procedure which can readily be used to determine if a visor meets military specifications concerning its optical properties, particularly the spherical power and prismatic deviation of the visor.
Consequently, a need exists for easy-to-use, reliable procedures for measuring optical properties of transparencies, such as helmet visors.